The present invention relates to a shift device that electrically controls shifting of a number of gear ranges of an automatic transmission installed in a vehicle.
The gear ranges of an automatic transmission for a vehicle, such as a P (parking) range, an R (reverse) range, an N (neutral) range, and a D (drive) range, are switched by a manual valve. A shift device for the automatic transmission includes a shift lever. When the shift lever is manipulated, the shift lever moves between gear positions located in order on a substantially straight line. The shift lever is directly connected to the manual valve through, for example, a link or a wire mechanically. Therefore, a manipulation force greater than or equal to a predetermined value is required to switch the manual valve by the manipulation of the shift lever. Thus, to apply the principle of leverage, the length of the shift lever needs to be greater than or equal to a predetermined value. In such shift device, the shift lever is only manipulated linearly and requires a large space for manipulating the shift lever. Also, the installation position of the shift device is limited to a place where a link or a wire can be arranged, such as on the floor adjacent to the driver's seat or on the steering column.
To reduce the force required for manipulation and to reduce the size of the shift device, a gear shifting device for an automatic transmission is proposed in Japanese Examined Patent Publication No. 63-37729. According to the device of the above publication, a manual valve in the automatic transmission is controlled by a wire to shift drive gear ranges. The wire is driven by an electric motor and the electric motor is actuated in accordance with the manipulation of a number of electric switches.
According to the shift device structured as above, a driver can shift the gear range of the automatic transmission by manipulating the electric switches with a small force and the size of the shift device is reduced. Also, the shift device is not required to be mechanically connected to the automatic transmission. Therefore, the shift device can be located at any position in the passenger compartment.
However, to reliably select a desired gear range of the shift device of the above publication, the electrical switches must be manipulated carefully. This hinders the operability of the shift device.
To solve such problems, Japanese laid-open publication No. 3-157557 discloses a gear shifting device for an automatic transmission. The gear shifting device is provided with a shift device, which has a stroke contact type manipulation switch. The contact points of the manipulation switch are located adjacent to one another along a predetermined track. Since the shift device of above publication is provided with the stroke contact type manipulation switch, the size of the shift device is reduced and the shift device can be placed at any position. According to the above shift device, a driver can confirm the current gear range by a gear range indicator arranged on, for example, an instrument panel. Thus, the drive can manipulate the manipulation switches intuitively.
However, the shift device of the publication No. 3-157557 is provided with the stroke contact type manipulation switch and the manipulation positions are located adjacent to one another along the predetermined track. Therefore, if a driver manipulates the manipulation switch too fast, the switch could slide past a desired manipulation position. Therefore, a driver cannot manipulate the manipulation switch promptly. Thus, the operability of the shift device is insufficient.
The objective of the present invention is to provide a miniaturized shift device that has an improved flexibility of installation position and an improved operability.
Further objective of the present invention is to provide a shift device that prevents the assumption of a driver related to the setting of a gear range of an automatic transmission being different from the actual state of the gear range so that the driver is not disturbed.